Steam Jet Ejector-Principal

Steam jet ejector is a device for producing vacuum which is achieved by using a high-pressure motive steam. the primary advantages of steam jet ejector are simplicity of operation, no mechanical drive and has no moving parts.

Typically steam jet ejector has three parts; the jet nozzle (2), the suction chamber (3) and the diffuser (4,5,6). the figure 1 illustrates basic operation principle of the steam jet ejector.

  • Figure 1: Basic structure & flow model of Steam Jet Ejector
  • Figure 2: Flow Model of suction flow

We have produced numerous improvements in steam jet ejector design and test results. Left figure illustrates suction capacity which calculated by computer at entrance of diffuser. Suction capacity at left figure is 133 kg/hr which corresponds to minimum value to the curve.

Sometimes there is no minimum value, in this case, eddy current occurs and suction capacity decreases suddenly (By professor Ueda).


  • Simple Structure and trouble free
  • Low maintenance cost and long life
  • No mechanical drive & no moving parts
  • Low installation cost
  • No limit to the capacity
  • Explosion proof construction

Steam jet ejectors are used in field:

  • Steam power plants: Vacuum pump for surface condenser
  • Petrochemical: Distillation, deodorization plants
  • Synthetic fiber: Polymerization of polyester fiber
  • Food: vacuum dryer
  • Paper: Thermo Compressor
  • Ship building: Crude oil stripping pump
  • LPG Terminal: jet condenser
  • Steel industry: Degassing unit for RH, DH, TD, LD
  • Environmental: Thermo Compressor
  • Pharmaceutical: Frozen dryer

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